Pulse-translating system



5 Sheets-Sheet 1 .admi

Aug. 23, 1960k R. BJ. BRUNN y 2,950,463

PULSE-TRANSLATING SYSTEM Filed June 8, 1954 5 Sheets-Sheet 2 Desired Code I I L I L Code d Spucipgs n Incorre DI Codes m-Il Vl FlG.2c|

| I* "L I 1I Il Il I -I-I l l l ml I l l 1 :Leading l I l I-I l l l III l z I I .m l l n l n i :Inerleuved i l l l l l l l! l I l l E E 5 VI e i E smmdled Time-l- Aug. 23, 1960 R. B. J. BRUNN PULSE-TRANSLATING SYSTEM 5 Sheets-Sheet 3 Filed June 8. 1954 o m o o o o o o Time FIG2C Amplitude Aug, 23, 1960 Filed Junev 8. 1954 R. B. J. BRUNN I ULSE-TRANSLATING SYSTEM Nullifes effec? of Pulse d (Wrong 2nd vpulse of 2nd pair c+d) and pulse c (Wrong 2nd pulse of Ist pair :I IIIcl rIc- III l l 2| ITI I ITC VII I IIa I I I I I I I rrd I IIC III I m i .g 'I I I I I I I I 2| I III I l-I`I= I`|^I l I`|`a-t I I +l l| l I I i d '.I b I l I OUT I VI? II I II I I I I +I I I -I I I I I I I I I I I I ol E l I I I I I l E I I I I I uw: Imc: I I I I I l .I I I ii I IIIHII IIIHCI I I I I I 0l I I I I I l I I I I l I b| l l l -I I LIIIIIII .IIJSI I I I I I DI l|b+d b-Ic:l .I I I I I I a-I-cI I I I I l appearing ai poinIs'Band 5. I I I I I i I I I I I I I I I I I I 0| I I I I I I I I I I I I b+d I a+c I i I I I l I I b+C| I I I I Nullifies effect of puIse b (Wrong lst pulse of 2nd I pair b+d and pulse a( Wrong Ist puIse of Ist pair a+c)| appearing aI pinis Band 5. I IV l I I I I I I I oI I I I I I I I I l l l I I U l I I-I I I I I I I I I I I :l I I I I I I I I l I IJ I I E f I I I I I' III III I I i N I I9 f8 te 15 t3 I2 i'I o Tmef i FIGA 5 Sheets-Sheet 5 "I I-IsI Code 111 2nd Code E Poin 2 Point 3 Pain? 4 Poin 5 PoInI s (I+5) PoinI 7 (2+5) Point 7 Delayed Poim 9(4+5 +7 Delayed) POInI Io .Concidence) PoinI II (6I-5) Poin l2 insana Patented Aug. 23, i960 SEATING SYSTEM Filed June 8, 1954, Ser. N0. 435,339

14 Claims. (Cl. 340-164) General The present invention relates to pulse-translating systems and, more particularly, to pulse-translating systems .which are capable of developing an output signal in response to wanted pulse combinations having a desired spacing while discriminating against unwanted pulse combinations occurring `at random but which may have the desired spacing. Such systems are often referred to as decoders and have particular utility in the distancemeasuring equipment used in aircraft navigation systems. Accordingly, the invention will be described in that environment.

One important requirement in aerial navigation is the determination lof the distance between an aircraft in ilight and known geographic points along the line of ilight. Distance-measuring equipment has been employed in aircraft to provide a pilot with an indication of the distance between his aircraft and such points. Modern airborne equipment usually comprises a transmitter for transmitting coded pulses for interrogating selected terrestiially located responder beacons along the line of flight. individual ones of these beacons may respond only lto pulses corresponding to their particular interrogating code by transmitting coded reply pulses for use by the distance-measuring equipment on the aircraft. Desired reply pulses actuate the coding apparatus in the distance-measuring equipment and a voltage is derived which is representative of the round-trip propagation time between the aircraft and the responder beacon. It will be evident that the magnitude of this voltage changes in accordance with the relative movement between the aircraft `and the beacon.

in order to utilize the coded reply pulses of a selected beacon which is being interrogated by the moving aircraft, the distance-measuring equipment is provided with a searching system which is effective to place the equipment in a state of selective response tot the coded-reply signals from a selected responder beacon. To accomplish searching, distance-measuring equipment includes a receiver having a received-signal-translating channel that is normally blocked and a gated circuit therein for conditioning the channel Ito translate pulses which may be received within a short gating interval. Varying the time relation of the gating interval relative to the transmission of the interrogating pulses from the distance-measn uring equipment is effective to achieve searching, as will be clear from a consideration of the following example. Assuming that the receiver is gated or conditioned to translate pulses lwithin a short interval after the interrogating signal is sent out and that a reply signal is returned directly, as in the case where the aircraft is very close to the beacon, the beacon reply is accepted and a distance indication is obtained. If the reply should be delayed beyond the duration of the short gating interval, thus representing a greater separation of the yaircraft and the beacon, that reply is not accepted. However, delaying the gating interval relative to the transmitted interrogation may condition the receiver to accept the delayed reply and allow the distance-measuring circuits to provide an indication of a greater distance from the aircraft to the beacon. When a reply has been found, the search is discontinued and a tracking system is energized to keep the reply within the gating time to facilitate an accurate determination of distance.

The distance-measuring equipment includes coding'and transmitting `apparatus for interrogating any selected one of a plurality of responder beacons and also includes suitable decoders which, for the most part, select only coded reply pulses (such as paired pulses having a predetermined spacing) received from the selected responder beacon, thus materially reducing the possibility ofthe searching operation being interrupted by interrogating or challenging pulses received fromv nearby aircraft or by reply pulses'from a beacon or beacons which responded to those challenges. However, in regions of heavy aircraft trafc, those pulses may occur at random and a bunching of the random pulses produces undesired pulse combinations having a spacing corresponding to the interrogating code and to the reply code of the interrogated beacon. These undesired pulse combinations constitute a pseudo desired signa which is actually a false signal that is not rejected by the conventional pulse-tuansrlating system or decoder in the receiver of the interrogating aircraft or in the decoder in the receiver of the responder beacon and undesirably (a) increases the search time of the distance-measuring equipment by unnecessarily interrupting the searching operation, (b) places a large power demand on the transponder beacon by increasing its duty cycle, and (c) lowers the over-allefliciency and performance of the distance-measuring equipment in regions of heavy aircraft traffic where eticiency and performance are more important considerations than in regions of light trac.

Heretofore, it has been customary to regard the random undesired pulse combinations having the desired spacings yas being unavoidable and to base the performance of the distance-measuring equipment of an air navigation system on probability calculations wherein the undesired signals are treated as a random phenomenon.

It is an object of the invention, therefore, to provide a new `and improved pulse-translating system or decoder which avoids one or more of the above-mentioned disadvantages a'nd limitations of prior such systems.

lt is another object ofthe invention tov provide a new and improved pulse-translating system for use in the distance-measuring equipment of `a navigation system to improve the efliciency and the performance of that navigation system.

lt is a further object of the invention to provider a new and improved puise-translating system which responds to wanted pulse combinations having a desired spacing while discriminating against unwanted pulse combinatio-ns occurring at random but which may have the desired spacing.

It is an additional object of the invention to provide a new and improved pulse-translating system which is particularly useful in `responding to paired pulses having a desired spacing while discriminating against unwanted paired pulses occurring yat random but having the desired spaclng. v In'accordance with a particular form of the invention, a pulse-translating system comprises an input circuit for supplying desired pulse groups having a given pulse spacing and subject to the translation of a plurality of other pulse groups which may combine iat random to produce undesired pulse groups having the aforesaid given spacing. The pulse-translating system also includes a pulsetranslating network coupled to the aforesaid input circuit v 3 and including a control device and a pulse-selector circuit responsive to the desired pulse groups for deriving therefrom a desired output signalbut which tends to respond toand develop from the undesiredpulse groups an undesiredoutput signal. The pulse-translating circuit further includes a meansincluding control apparatus coupled to the pulse-translating network and the control device and effectively responsive to pulses of the aforesaid other pulse groups for deriving and applying to the control device a control signal which momentarily places the network in a non-translating condition, whereby the system has a reduced tendency yto develop the undesired output signal while deriving the desired output signal. I

For a better understanding of the present invention, together with other and further' objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and itsV scope will be pointed out inthe appended claims. Y. f

' IReferring tothe drawings:

Fig. l is schematic diagram of a transponder beacon and an interrogator-responser of a radio-position locator or distance-measuring system which includes a pulse-translating system in `accordance with the present invention;

Fig. 1d is a circuit diagram of the pulse-translating system represented schematically in Fig. l; Y

Figs. 2cv-2c, inclusive, are graphs utilized in explaining the operation of the pulse-translating system of Fig Fig. 3f is a schematic diagram yof `a modified form of the pulse-translating system of Fig. 1; j

Fig. 3a is a circuit diagram off the Fig. 3 pulse-translating system, and

Fig. 4 is a graph useful in understanding the operation of the Fig. 3a system.

VDescription of Fig. 1 distance-measuring system including pulse-translating system or decoder 40 Referring now more particularly to Fig. l of the drawings, there is represented a distance-measuring system including a transponder beacon 20, which may be terrestrially located, that includes a receiver 21 which is coupled in cascade with a Vdecoder 22 of suitable construction, a coder 23, and a transmitter 24. transmitter 24 are coupled to a common antenna system 25..

. The distance-measuring system also includes a distancemeasuring equipment or interrogator-responser 30,'which will be assumed to be installedin an aircraft in flight, that includes means for transmitting coded periodic time-reference pulses such'as paired pulses and for receivin'gposition-representative delay pulses, which also may be coded pairedpulses, from the terrestrially located transponder beacon lf2.0. Thetransmitting means of the interrogatorresponsert) includes a timer 31 coupled to a transmitter 32 for supplying periodic timing pulses thereto. A `coder 33 is'coupled to a pair of input terminals 38, 38 of a searching and tracking apparatus 34'for supplying control pulses thereto. A suitable searching and tracking apparatus for the unit 34 is described and claimed in Patent No. 2,491,029, granted December 13, 1949, to R. B. JQ

Brunn, and entitled System for Translating Pulse SignalsY of Variable Time Delay and4 in the copending application of C. J. Hirsch, Serial No. 186,843, filed September 26,

1950, 1and entitled Control System. The'output terminalsV 39, 44 of the searching and tracking apparatus 34 are coupled to a distance indicator 35 of suitable construction. The coder 33 is also coupled to the transmitter 32 for supplying periodic'. pulses of positive polarity which are delayed-with reference to the pulses from the timer 31. The transmitter 32 is. designed to transmit periodictime-reference pulses in the form of wave-signal pulses of predeterminedduration and spacing representative ofa particularV interrogating codeof the interrogator-responser 30. VThe latter also includes a receiver 36 coupled to an antenna system V37 commo-n to the transmitterV and the receiver thereof. An output circuit of the transmitterrmay be coupled to the receiver 36 for supplying thereto negativepolarity disabling pulses to disable the receiver each time the transmitter develops a rtRlio-frequency pulse for application to the antenna system 37.

IInterrogator-responser 30 of the distance-measuring system further includes a pulse-translating system or decoder 40 having a pair of input terminals 41, 4l coupled to the output circuit of the receiver 36 and having'a pair of output terminals 42, 42 coupled to two pairs of input terminals 43, 44 and 45, 44 of the searching and tracking apparatus 34. The units thus far described, with the exception of the decoder 4t) which is constructed in accordance with the present invention and will be described in detail subsequently, may be of conventional construction and operation so that a detailed descriptionV and explanation of the operation thereof are unnecessary.

in considering briefly the general operation of the described distance-measuring system as a whole, it will K be assumedinitially that the decoder 22 of theV beacon 20 translates paired pulses having a particular spacing.

established by the coder 33 of*interrogator-responser 30 and that the Idecoder of interrogator-responser is conditioned to translate paired pulses having a spacingestabn lished by the coder 23 of beacon 20. Each timing pulse The receiver 21 and the which develops paired radio-frequency Vpulses for appli-V cation to and radiation by the antenna system 25. VThese which the timer 31 applies to the transmitter 32 causes the ,latterv to `develop a iirst radio-'frequency pulse for radiation by the antenna system Y3'7. A predetermined time interval-after each timing pulse is applied thereto, the coderV 33 develops a second timing pulse for application to the transmitter 32 and simultaneously develops another timing pulse of suitable polarity for application tothe input terminals 3S, 38 of the searching and tracking ,deviceVS-E- for controlling the operation of the sweep circuits thereof. The timer 31 and the coder 33 are, therefore,'eii`ective to apply a series of paired timing pulses to the transmitter 32 and the spacing between individual pulses of a pair is determined by the parameters of the coder 33. The transmitter 32V similarly develops the second radio-frequency pulses of the pairs and applies vthem to the antenna 37 for radiation thereby.

Simultaneously with the generation of each radiofrequency pulse, theV transmitter 32 generates a control pulse'for disabling the receiver 36 at least during the Vtransmission intervals. t Y

Vpulse in response to each coded pair for application t0 the coder 23. The coder is effective to develop pairs of triggering pulsesV for application to the transmitter 24 radio-frequency pulses are intercepted by the antenna system 37 and are applied to the receiver 36 Vwhich, develops an output pulse of negative polarity for each received,radio-frequency pulse and applies that output pulse to theinput terminals 41., 41 of the pulse-translating system or decoder 40. i f Y The decoder 4t) effectively develops at its output ter- 1ninals42, `42a single output or control pulse in response When to each applied pair having the correct spacing. a sufficient numberV of consecutive control pulses are applied to the terminals 43, 414 and 45, 44 of the searching and tracking apparatus 34 in conjunction with pulsesr appliedV toterrninals38, 33 thereof from the'coder 33, in the mannermore fully explained in the above-identified patent and copending npplication, the apparatus 34 operates in its tracking mode and producesan output signal for application to the distanceV indicator .-35 which is'then effective to yprovide a continuous indication of the vary- Y ingdistance between the .airborne interrogator-responser tland Itheground beacon 2t?. Assuming for the moment that the receiver 36 fails for a brief interval to intercept .r 'in the paired radio-frequency pulses radiated by the transponder beacon Ztl for some reason such as an obstacle in the propagation path between the beacon and the interrogator-responser 30, the apparatus 3'4 will operate in its searching mode until a series of paired radio-frequency pulses having the desired spacing are received by unit 36.

Other aircraft carrying interrogator-responser units similar to unit 30 may be flying in the vicinity of the terrestrially located beacon 20 and may be attempting to interrogate that beacon by means of paired pulses. These paired interrogating pulses may have spacings which are quite different from the code spacing of the interrogatorresponser 30 and they may represent undesired pulse groups or combinations which may undesirably influence the operation of the searching and tracking apparatus as controlled by the decoder 40. These undesired pulse groups may occur at random and may be so interleaved or otherwise arranged in time as to create random pulse pairs having a pulse spacing which would be accepted by a conventional decoder that might be connected in circuit in lieu of the decoder 40. Such a conventional decoder would respond to at least some of the undesired pulse groups and produce a series of output pulses which would cause the searching and tracking apparatus 34 to' track for a short period of time when it should be searching for a reply from the beacon 20. This erroneous mode of operation would be undesirable for reasons already stated. The Adecoder 4th in accordance with the present invention is elective materially to reduce the possibility of translating undesired pulse groups which might undesirably affect the proper operation of the searching and tracking unit 34.

Description f pulse-transating system or decoder 40 of Fig. 1

Referring now more particularly to the pulse-translating system or decoder 4d' of Fig. 1, this system includes an input circuit comprising the terminals 41, `41 and the electrical connections associated therewith for supplying desired pulse groups having a given pulse spacing and subject to the translation of a plurality of other pulse groups which may combine at random to produce undesired pulse groups having the aforesaid given spacing. Paired-pulse groups are commonly employed in presentday distance-measuring systems. Accordingly, the invention will be described and explained in connection with the use of paired pulse groups although it will be understood that decoders of the type under consideration may be designed to accommodate other multiplepulse groups.

The decoder 4u includes a pulse-translating network 46 coupled to the input terminals 41, 41, which network comprises a time-delay means or time-delay network 47 which aords a very short delay to translated signals, a control device in the form of a normally closed electronic switching device 43, a time-delay means preferably in the form of a one-way time-delay network 49 having a plurality of network sections to be described more fully subsequently, and a pulse-selector circuit in the form of a coincidence detector or repeater 5@ coupled to one of the network sections. As will be explained hereinafter, the network 46 is responsive to desired pulse groups or paired pulses for deriving therefrom in the output circuit of the coincidence repeater 50 a desired output signal but which tends to respond to and develop from the aforesaid undesired pulse groups an undesired output signal. The output circuit of the coincidence repeater 50 is coupled to the output terminals 42, 42 of decoder 40. The time-delay network 49 includes winding portions equal in number to the pulse combinations which are likely to be used in the distance-measuring system and, hence, are likely to be received by the receiver 36. To facilitate the explanation and understanding of the present invention, it will be assumed that the receiver is likely to apply to the decoder four dierent types of pulse groups comprising paired pulses having a given or Vcorrect pulse spacing, and also to apply three other types of pulse groups comprising paired pulses having incorrect spacings but which may combine at random to produce undesired pulse groups, at least some of which have the correct pulse spacing. For example, the distance-measuring system may be considered to employ paired pulses having 5, 10, 15, and ZO-microsec'ond spacings for communication between one or more transponder beacons such as beacon 20 and a plurality of airborne interrogator-responsers such as unit 30. The interrogatorresponser in the drawing, however, is assumed to have a decoder 4i) which is intended to translate paired pulses having a 10-microsecond spacing but is intended to discriminate against paired pulses which have 5, l5-, and ZO-microsecond spacings and which may combine at random to produce some undesired paired pulses having a 10-microsecond spacing. These paired pulses and various combinations thereof will be considered in greater detail subsequently in connection with Fig. 2 of the drawings.

The time-delay network 49 includes four cascaded winding portions 51., 52, 53, and 54 each providingva time delay of 5 microseconds to an applied signal. For convenience, the terminals of the cascaded portions are designated as points, 4, 5, 6 and 7. Points 3 and 5 are connected to different input terminals of the coincidence repeater Sil, which terminals may, for example, comprise diterent control electrodes of a multielectrode tube that is normally biased to anode-current cutoff and has its cathode grounded while its anode is connected to the ungrounded one of the output terminals 42, 42.

The decoder additionally includes means including a control apparatus having individual input circuits coupled to predetermined portions of the time-delay network 49' and having individual output circuits coupled to the control or switching device 48 and eiectively responsive to pulses of the other pulse groups, namely to the three pulse groups of paired pulses having 5-, 15, and 2,0- microsecond spacings, for deriving and applying to the device 48 a control signal which momentarily places the pulse-translating network 46 in a non-translating condition, whereby the decoder 40 has a reduced tendency to develop an undesired output signal at the terminals 42, 42 while deriving the desired output signal. This control apparatus includes three coincidence repeaters 55, 56, and 57 which preferably are similar to the repeater 56 and have corresponding input electrodes individually coupled to respective ones of the points 4, 6, and 7 on the timedelay network 49. The other input electrodes of these three repeaters are coupled through a polarity-reversing `amplifier 58 to a point 1a which corresponds with the ungrounded one of the input terminals 41, 41. 'Each of the input electrodes just mentioned is connected to a point 1 as represented in Fig. 1. The loutput electrodes of the repeaters 5v5-57, inclusive, are coupled to a suitable circuit of the switching device 48 for applying a control or disabling pulse of negative polarity thereto. The terminal of the time-delay network 47 which is remote from point 1a is designated as point 2. The time-delay network 49 is terminated at its remote end or point 7 by a resistor 59 having a value equal to the characteristic` impedance of the network for the purpose of preventing reiiections from point 7. The resistor 59 is connected to a biasing source indicated as C for the purpose of normally maintaining each of the coincidence repeaters S0 and 55-5'7, inclusive, in a nonconductive condition.

General explanation of operation of pulse-translating system 40 of Fig. 1 Y Y Prior to a detailed consideration of the circuits of the various units of the decoder 40 and the operation thereof, a general explanation of the operation of the decoder 40 of Fig. 1 will be helpful. Assuming first that a desired pair of pulses having a lO-microsecond spacing is applied to the input terminals 41, 41, those pulses are translated by time-delay network 47 which imparts a very short time delay thereto prior to their application to the switching device 48. Since the switching device 48 is normally closed, it translates the applied pulses to the input circuit of the time-delay network 49. The iirst pulse of the pair traverses the network section comprising portions 51 and 52 and, after an interval of l0 microseconds, is applied through point to an input electrode of the coincidence repeater 5'0 at the same time that the secondv pulse of the pair is applied through point?, to the other input elect-rode of that repeater. The simultaneous application of these two pulses to the normally non-conductive coincidence repeater renders it conductive so that it translates through its output circuit to terminals 42, 42 an output pulse ofV negative polarity for controlling the unit 34. Successive paired pulses of lO-microsecond spacings are effective to derive output pulses in the manner just explained.

Let it now be assumed that paired pulse groups having spacings of 5, 15, and `microseconds are` applied to the terminals 41, `41 and that these paired pulses might combine at random to produce undesired or false paired pulses having the correct lO-microsecond spacing.

VAssuming now that V'such pulses are traversing the timedelay network 49 and that a pulse pair having a Sc-rnicrosecond spacing is applied to the network section 51, theV 1 to the otherinput electrode of the coincidence repeater 55. Network 47 affords a slight delay to the signal translated by it yto compensate for the iinite time required Vfor the amplifier 58 to translate an applied pulse to the normally nonconductive coincidence repeater 55. When the repeater 55 is momentarily rendered conductive, its anode potential decreases and a negative polarity pulse is applied to the switching device 48 momentarily to disable it or cancel any output signal which it would tend to develop. Thus, the second pulse of the pair with'the 5- microsecond spacing may be consideredV effective momentarily to place the device 48 in a nontranslating condition so that the second pulse cannot be applied by point 3 to the coincidence repeater 5t) 'in coincidence with any preceding pulse which might then have traversed the time-delay network 49 to point 5 and to the other input electrode of the coincidence repeater. 50. The pulsetranslating network 46 and the control apparatus or coincidence repeaterSS may be considered -toY be effective, with reference to undesired pulse groups which include paired pulseshaving S-rn'icrosecond 'spacingsg toy prevent all second' pulses of unwanted pairs from cornbining in any way to produce an output signal. However, they will not preventthe first pulse of an unwanted pairV from acting conjointly on'the coincidence repeater 50V with a pulse which was earlier intime to cause that repeater to develop afalse output pulse.

- Similar paired pulses with a l5-microsecond spacing Fig. la is a circuit diagram of the various circuit ele-` ments represented schematically in Fig. l. Corresponding elements `in the two figures are represented by the same reference numerals. The switching device 48 comprises a triode 64.) having its cathode grounded and its control electrode connected directly to the output terwill be effective at the time of the second pulse Vthereof to render the coincidence repeater 56 Aconductive so that its-output signal effectively `disables the switching device 48 at the time of the second pulse.

- preceding pulses that are being translated by the timev delay network 49 to develop output pulses at the times of occurrence of the second pulses Vof the undesired pairs. Consequently, the *decoder discriminates against many un- Likewise, pairedY pulses Vwith a ZO-mic'rosecond spacing render the coinci- Thus, the decoder 49 discriminates fier 5S. Y

also 'coupled to the cathode of a diode 71 having itsV minal 2 of 4the time-delay network 47 while being connected to ground through a grid-leak resistor 61. The latter preferably terminates the network 47 in its characteristic impedance to avoid reflections. The anode of the triode 6@ is connected toa source of potential -l-B through an anode load resistor 62 having a value preferably equal to the characteristic impedance of Vthe timedelay network 49. The anode'of triode 6i) is coupled to point 3 representing the input terminal to network 49 through a coupling condenser 64. The coincidence repeaters 55, Siti, 56, and 57 preferably comprise pentodes 65-68, inclusive, having their inner control electrodes coupled respectively to points 4, 5, 6, and 7, their cathodes connected directly to ground, and theh screen electrodes connected in a conventional manner to a source of potential +Sc. The anodes ofthe tubes 65, 67, and 68 are connected through points 8,' lil, and 11 and a load resistor '70 Vto a source of potential -l-B while the suppressor `or outer control electrodes thereof are interconnected and are coupled through a resistor 69 to a source of bias potential C which, with the bias on thesuppressor electrodes of the tubes, is effective normally to maintain the tubes in a non-conductive con'- dition. The suppressor electrodes are connected to the points lyand are also coupledV through a condenser 73 tothe anode of a tube '72 of thepolarity-reversing ampli- The anodes of the tubes 65, 67, and 63 are anode; connected directly to the anode or the tube 6i) of switching device *45.

The anode of the tube 66 of the coincidence repeater 5@ is coupled to the ungrounded one of the terminals 42, 42 and is also connected to a source of potential -l-B through a load resistor '76. The cathode of tube 66- is grounded, the screen electrode is connected to a source -l-S in a conventionall manner, and the suppressor or outercontrol electrode is connected directly to point 3 of the time-delay network 49. The source -C, which is connected to the control electrodes of the tubes 65-58, inclusive, through resistor E9 and the network sections 54, 53, '52, and '51, is eifective'with the bias on the vsuppressor electrodes normally to maintain the repeaters in a nonconcluctive condition as previously mentioned. The anode terminals of` the tubes 65268, inclusive, are designated respectively as points 8, 9, iii, and lll. The control electrode of the tube 72 is connected to point 1a and is also connected to ground through afgrid-leak Explanation of operation of pulse-translating system 0 decoder 40 of Fig. la I In considering the operation of the decoder of Fig.

V1a, reference will be made to the various curves of Figs.

Zit-2c, inclusive.V Fig. Zai-represents four different individual paired pulse combinations which might be applied to the input terminals 41,' of the decoder. fCurve I represents 'the desired code wherein the paired pulses have aV IO-nu'crosecond spacing, curve'll represents paired pulses having afS-microsecond. spacing, curvey lII represents pulses having a 15-microsecond` spacing, and `curve iVrepresents a third'pair of pulses having Va ZO-microsecond spacing. As previously mentioned, curves II, III, and IV are incorrect codes.

To facilitate understanding the manner in which it is possible for paired pulses having an incorrect pulse spacing to combine to develop another pair of pulses having the correct pulse spacing, Fig. 2b delineates three such combinations. Two pairs `of pulses having a S-microsecond spacing as in curve il of Fig. 2a are represented wherein one pair of pulses leads the other. It will be apparent that the leading and the trailing pulses of each of the different pairs can combine to produce two undesired pairs having a lll-microsecond spacing corresponding to that of the desired code represented by curve I of Fig. 2a. Similarly, two pairs `of pulses having l5-microsecond spacings as in curve III of Fig. 2a may be interleaved so that both the first pulses and the second pulses of the different pairs combine to provide undesired pairs with the correct spacing. Likewise, a pair of pulses having a ZO-nrierosecond spacing as in curve IV of Fig. 2a may straddle a second pair Yof pulses having a S-microsecond spacing as in curve II therein so that the first pulses of the different pairs effectively form an undesired pair having the correct spacing. Also the irst pulse of the second pair and the second pulse of the first pair effectively form an undesired pair with the correct spacing. It will be understood that numerous `other combinations are possible and those which have been described above are only illustrative of some of the possible combinations.

Referring now to Fig. 2c of the drawings, it will be seen that the abscissa yor time axis represents later moments of time, such as f1, t2, and t3 as being farther to the left. The legends on the right in Fig. 2e designate the code of applied paired pulses and the points in decoder 4t) where the illustrated series of pulses appear. There is represented a :first pair of pulses a, c having a 15-microsecond spacing corresponding to the incorrect code III of Fig. 2a. There is also represented a second pair of pulses b, d which are interleaved with the pulses a, c and have a lS-microsecond pulse spacing also corresponding to the incorrect code of curve III of Fig. 2a. When these two pairs of pulses are applied to the input terminals 41, 41 of the decoder 4d` of Fig. la, they appear at point 1a as a series of pulses rz, b, c, and d having leading edges occurring at times to', t2', t3', and t5. After a short time delay has been imparted thereto by the time-delay network 47, the pulses just mentioned appear at point 2. with leading edges occurring at times to', tz, t3, and t5 as shown in Fig. 2c. After translation through the normally conductive tube 6% of the switching device 4S, this series of pulses would appear at the point 3 corresponding to the input terminal of the time-delay network 49 as represented. The pulses c and d represented as appearing at point 3 in Fig. 2c are shaded for a reason which will be explained subsequently. Since each of the network sections 51, 52, 53, and 54 of the time-delay network 49 imparts a S-microsecond time delay to pulses applied thereto, the series of delayed pulses appearing at points 4, 5, 6, and 7 may be represented as indicated in Fig. 2c near those legends. The pulse pairs c and d appearing at points 4, 5, 6, and 7 are also shaded for reasons which will be stated hereinafter. The series of negativegoing pulses appearing at point la is amplified and reversed in polarity (and delayed slightly by the amplifier S) to form positive-going pulses as represented ad jacent the legend for point l in Fig. 2c.

Let us now consider the action `of the coincidence repeaters 55, 56, and 57 in conjunction with the switching device 48 in discriminating against at least some of the pulses which are applied to point la of the decoder. The tube 65' of coincidence repeater 5S develops at its anode or point 8 a negative-polarity output pulse when coincidence of the pulses applied to points 1 and 4 occurs. Referring to the pulses delineated in Fig. 2c as appearing at points v1 and 4 it will be seen that at time t3 coincidence Occurs for the pulses b and c so that there is developed at point 8 a negative-going pulse identiiied as' b-l-c. Referring back to the series of pulses delineated as appearing at point 3, it will -be Seen that the positive-going pulse c is applied to point 3 from the anode of tube 60 through the coupling condenser y64. This positive-going pulse coincides in time with the negative-going pulse effectively applied from point 8 through the diode 71 and the condenser 64 to the aforesaid point 3. The magnitudes of the two applied pulses are such that a cancellation effectively occurs. Accordingly, the shaded pulse c represented as appearing at point 3` does not actually exist and, hence, cannot be translated along the time-delay network 49 to points 4, Si, 6, and 7. In each instance, therefore, the pulse c which might otherwise exist at points 4, 5, and 6 is represented in Fig. 2c as being shaded to indicate that this pulse actually does not exist. The cancellation of the pulse c at point 3` electively means that the second pulse of the iirst pair of pulses a and c having a l5-microsecond spacing as represented by the irst curve.

of Fig. 2c cannot combine with a second pulse of another pair such as pulse d represented in the second curve of will be developed by =a standard decoder.

Fig. 2c to produce an erroneous output signal.

Coincidence repeater 50 accepts those pulses appearing at point 3 which are in coincidence with those pulses appearing at point 5. From the curves of Fig. 2c it will be seen thatpositive-going pulses a and b applied to points 3 and 5 are coincident `at time t2 and are effective to render the tube `66 conductive, thereby developing at point 9 an output pulse of negative polarity for application to the output terminals 42, 42. Thus, the decoder 40 decodes on pulse b, shown in the second curve of Fig. 2c, which comprises a iirst pulse of an incorrect pair of pulses a-i-b. This represents an erroneous output signal but constitutes only one erroneous output pulse out of a possible two combinations for the situation presently under consideration.

The coincidence repeater 56 responds to coincident positive-going pulses 'appearing at points ll and 6 and these coincidences `occur lat times t3 `and t5. Tube 67 is rendered conductive at these times and develops at point 1li a pair of negative-polarity pulses which are the refrom point It) by the diode 71 and the condenser 64 and is effective to cancel a positive-going pulse appearing at point 3 -at time t5. Accordingly, the pulse d represented as appearing at point 3 has been shaded to denote that it is nonexistent. It will be clear that pulse a', therefore, cannot appear at points 4, 5, 6, and 7.

The output signal appearing at point Il of the coincidence repeater 57 is produced by any pulses which appear at point 7 in coincidence with pulses present at point 1. Since no such coincidence occurs, no output signal appears at point 11 as represented by the third from the last curve of Fig. 2c.

From the foregoing explanation of the operation of the decoder with reference to two interleaved pairs of pulses wherein each pair has `a lS-microsecond spacing, it will be seen that the decoder develops but a single undesirable output pulse whereas a conventional decoder would derive a pair of undesired output pulses. It has been :determined that for other pulse combinations and spacings, the decoder of Fig. la 4is effective to reduce undesired output pulses to one-quarter of the number which While the operation of the decoder 40 has been explained in connection with the application to the input terminals 41, 41 thereof of interleaved paired pulses having a 15- microsecond spacing, it will be understood that it will discriminateiagainst other pulse groups such as those represented in Fig. 2b. Thus the decoder of Fig. la ma- 11 terially discriminates against pulse groups which might combine at random to produce undesired pulse groups having the desired spacing.

While the operation ofthe decoder 4t) has been Yerr-- plained in connection with .the translation of pulses through the time-delay network'd in the forward direction, that is from left toright in the drawing, pulses developed at intermediate points along the network may also travel in the reverse direction. By an analysis similar to that represented by Fig. 2c of the drawings, it may be shown that pulses which are translated in the reverse direction do not impair the performance of the decoder 4i). Diodes may be employed, if desired, between the various portions of the network 49 to avoid the translation of positive-polarity pulses in the reverse direction.

Description of pulse-translating system or decoder 40 of.

Fig. 3

Fig. 3 represents schematically a decoder similar to that ofFigs. l and la. Accordingly, corresponding elements are designated by the same reference numerals. The decoder of Fig. 3 differs from thatof Figs. l and 1r.'V in that the former is arranged to respond to the application of positive-polarity pulses to its input terminals 41, 4l, the switching device 453 is positioned near the output circuit of the system rather Vthan in the input circuit las in Figs. l and la, and the decoder includes a control apparatus which is somewhat diierent from that of Figs. l and la. The time-delay network lt-Sincludes four cascadcd portions 51454, inclusive, with a network section comprising network portions 53 and '54 that iatord a time delay equal to the desired-pulseV spacing.

For the purpose of explaining the operation ofthe decoder, it will he assumed that the individual network' portions just mentioned atord S-microsecond time delays v to pulsesv translated therethrough 4and that the :desired pulse spacing is 10 microseconds. The points 3 and 5 of network 49 are coupled to the input electrodes of theV coincidence repeater E@ which has its output circuit coupled to the cathode `of an isolating diode 91 having its anode terminal, which is designated as point 8, connected which are individually coupled `to individual ones of theY network sections. To this end, thetime-delay network 8i? includes portions 81-84, inclusive,"which have time delays corresponding to portions'Y Sl-Sli, inclusive, of the time-delay network 49. The time-delay network Si) is terminated at its output end by a resistor S6 having a value equal to its characteristic impedance, which resistoris connected across an inputcircuit of the switching device 4S. The opposite Vend ofthe network @u is terminated by a resistor 85 Vhaving a value also equal to the characteristic impedance of the network.'v An outaYV resistor 9% in another input circuit of the switching device 48, the terminals ofthe anodes just mentioned corresponding electrically with points 6a, 7a, and 9a represented in the drawing.n

The coincidence repeater Si?` responds to desired paired pulses of lthe proper spacing applied to its input circuits. The coincidence repeaters 55-57, inclusive, which respond to` pairedY pulses having incorrect spacings, have a Vcorresponding input electrode in each thereof connected to point Sat the remote end of the time-delay network 49. The other input electrodes of the repeaters 55-57, inclusive, are individually coupled to respective 'ones of points `l, 2, and 4 of the network 49.

General explanation of operation of pulse-translating vsystem 0r decoder 40 of Fig. 3

Prior `to a detailed considerationV of circuits of the various units o the decoder dil and the general'operationV thereof, a general explanation of the operation of vthe decoder 4d of` Fig. 3 will be helpful. Assuming rst that `a desired pair of pulses having a lO-microsecond spacing is applied to the inputr terminals 41, 41, those pulses Vare translated down the time-delay network 49 ,to its remote terminal 5. The iirst :pulse larrives at terminal 5 and is applied to an input electrode of the coincidence repeater 5G simultaneously with the occurrenceat point 3 and the application to the other input electrode of the second pulse of the properpair. The coincident application of positive-polarity pulses renders the repeater di? conductive anddevelops in its output circuit, for .application through the diode 91 to the switching device siii, a pulse of negative polarity lwhich conditions theY switching `device 4S to develop an output pulse of positive polarity which is amplied and translated to the output terminals 42, 42 as a negative-going pulse. Successive paired pulses having the proper spacings are eiiective to `develop-a series of output pulses Vat the terminals 42,42 in the manner just described.

It vwill Ynow be assumed'that paired pulse groupsV having `a spacing of 5, l5, `and 20 microsecondsare applied to 'the input terminals fil, 41 and that these paired pulses might combine at random to producey ftha-t the less delayed second pulse is `applied Ythrough point d to the. other input electrodejof the coincidence repeater, an outputpulse of negative polarity from ,unitV 57 Yrenders the double diode'39 momentarily conductive and one section of the diode applies that pulse through` Y incidene repeater Si?, as a result of the coincidence ofV the irst pulsepappearing at point 5 with a pulse being translated along the vnetworklil to point 3, isnot transv latedV to the-'output circuitV of the switching device 48.

put electrode of the coincidence repeater 55V is connected p to the Vinterco,nnec'ted cathodes. of" a double `diode 87,

one of 'the anodcs of which is connected to point 6 of thc-network Si). ,In a similar manner, a double diode 38 is connected betwecn'coincidence repeater 56. and point '7, and another double diode 89 Vis connected between coincidence repeater 57 and point'* of network Si). IheV r. disable it at that time.

Consequently, the coincidence repeater .57 may be said to discriminate Vagainst the rstV pulse of an improper pair having a 5-microsecond spacing. The negative-polarity pulsel which rendered the diode S9 conductive is also applied to point 9 and, after Va S-microsecond delay irnparted to thepulse Vby lthe network portion. 84, is applied by pointlt) across the resistor tok another input circuit Vof the switching deviced so as momentarily to l The translation of the negative polarity control'pulse froin'point 9 to point lil' occurs simultaneously with the translation of the second pulseof the unwanted pair from point 4 through network portion 54r of network 49 to point 5 thereof. Consequent-y ly, when the second pulse `of the unwanted pair reaches point for application to the coincidence repeater 50 at an instant when a positive-going pulse may reach point 3 from network portion 52 to condition the repeater 50 to develop a negative-polarity output pulse :for translation through the diode 91 to the switching device 48, the -latter is effectively disabled. Thus, it may be said that the decoder 4S prevents the second pulse of a pulse pair having this improper spacing from combining with another pulse of an unwanted pair to produce an erroneous output signal. Similarly, coincidence repeaters 56 and 55 and their associated circuits discriminate against both the iirst and second pulses of pulse pairs having and ZO-niicrosecond spacings,

whereby these pulses are inetective to combine at random to produce an erroneous output signal.

Description of pulse-translating system or decoder 40 of Fig. 3a

Fig. 3a is acircuit diagram of the various units represented schematically in Fig. 3. Corresponding elements in the two iigures are designated by the same reference characters. The coincidence repeaters 55, 56, 56, and 57 include pentodes 65-58, inclusive, having their input circuits connected to the time-delay network 49 as represented. The cathodes of the diodes 87, 88, 91, and 89, respectively, are connected to ground through resistors 94, 95, 96, and 97k and are coupled through suitable coupling condensers to the anodes or" the tubes 65, 67, 66, and 68. The anodes of these tubes are connected'to a source of potential +B through respective load resistors 70, 93, 76, and 94. The switching device 48 includes a pentode 98 which is normally conductive and has its cathode grounded, its screen electrode connected in a conventional manner to a source --Sc, and its anode connected to a source of potential +B through a load resistor 99. r[he anode of the tube 98 is also coupled through a coupling condenser 108 to the control electrode of a triode 191 having its cathode grounded and its control electrode connected through a resistor 'iZ to a biasing source -C which is effective normally to maintain the triode in a nonconductive condition. The anode of tube 101 is connected to a triode 193 having an anode load resistor 104 connected to a source of potential +B. The control electrode of the tube 163 is coupled to the anode of diode 91 and is also connected to ground through a gridleak resistor 185. The anode of tube 193 is connected to the anode of a diode 1% having its cathode connected to the ungrounded one of the input terminals of the amplier 92.

Explanation of operation of pulse-translating system 0r decoder 40 of Fig. 3a

In considering the operation of the decoder of Fig. 3a, reference will be made to the various curves of Fig. 4 to facilitate the understanding of this operation. lt will be seen from Fig. 4 that the abscissa or time axis represents the later moments of time such as times t1, t2, and t3 as being farther to theV left. The legends on the right in Fig'.V 4 designate the code oi the applied paired pulses and the points in the decoder 4t? where the illustrated series of pulses appear. Again, there is represented a rst pair of pulses a, c having a IS-microsecond spacing corresponding to the incorrect code lli of Fig. 2a. 'Ihere is also represented a second pair of pulses b, d which are interleaved with the pulses a, c and have a lS-microsecond pulse spacing also corresponding to the incorrect code of curve III of Fig. 2a.

When these two pairs of pulses are applied to the input terminals 41, 41 of the decoder 48 of Fig. 3a, they appear at point 1 as a series of pulses cz, b, c, and d having leading edges occurring at times to, t2, t3, and f5. After a short delay imparted thereto by network portion 52, the pulses just mentioned appear at point 2 with leading edges occurring at times t1, t3, t4, and t6. Network portions 53,

54, and 55 impart additional S-microsecond delays to the translated pulses so that the series of pulses appearing at points 3, 4, and 5 are as represented adjacent those legends in Fig. 4 of the drawings. Any output signals developed at points 6 and `6a by repeater 55 are a result of the simultaneousapplication of positive-going pulses appearing at points 1 and l5 to the input circuits of the tube 65 of the coincidence repeater 55. Since there are no coincidences of the pulses present at points 1 and 5, the signal developed at point 6 may be represented by the horizontal line shown in the drawings.

The signals appearing at points 7 and 7a by repeater 56 `are the result of the simultaneous application of the signals appearing at points 2 and `5, and from Fig. 4 of the drawings it will be seen that coincidences appear at times t4 and t6. The simultaneous application at time t4 of the positive pulse c at point 2 and the positive pulse a at point `5 to the coincidence repeater 56 renders tube 67 conductive and develops at its anode for application through the diode 88 to points 7 and 7a the negative polarity pulse a-l-c represented in the drawings for point 7. Similarly, the positive-going pulses d and b appearing at respective points 2 and 5 at time t6 actuate the coincidence repeater 56 and develop at points 7 and 7a the negative polarity pulse b-i-d represented as being developed at point 7 at time I6. The pulses which are developed at point 7, after being delayed 10 microseconds by network sections 82 and 83, appear at point 9 of the timedelay network 8i) with leading edges occurring at times t6 and t8 as represented in the drawings by the legend Point 7 delayed. The signal which is developed at point 9 results from the delayed signal just mentioned and the output signal developed at the anode of tube 68 of coincidence repeater 57 as a result of the coincident applica- -tion of positive-going pulses at points 4 and 5 to the input electrodes of tube `68. A coincidence of the pulses appearing at points 4 and y5 occurs only at time t6 and the positive-polarity pulses c and b occurring at those points at that time develop at point 9 the negative-polarity pulse b-l-c. The pulse b-i-c coincides With the pulse a-i-c translated to point 9 from point 7 through the network portions 82 and 83 and the two` pulses effectively may be considered as a single pulse. It will be noted in the curves for the pulses appearing at points 3 and 5 that at the time t6 no two positive pulses which are coincident in time are present. Accordingly, the iniiuence of the negative-polarity pulse which appears at point 9a at time t6 insofar as it alters the operation of the switching device 4S may be neglected.

The pairs of negative-polarity pulses which appear at point 9 at times t6 and t8 are translated through the net- Work portion 84 with a 5-1nicrosecond delay and appear at point 1t) at times t7 and t9 as represented in Fig. 4. Referring to the curves illustrating the pulses appearing at points 3 and 5 at time t7, it will be seen that two positive-polarity pulses c and d are applied by points 5 and 3, respectively, to the inner and outer control electrodes of the tube 66 of coincidence repeater 50. These pulses render tube 66 conductive and develop at its anode for translation through diode 91 a negative-polarity pulse which is applied at time t7 to point 11 at the control electrode of the tube 103 substantially simultaneously with the application from point 10 of a negative-polarity pulse to the outer control electrode of the tube 98. The two pulses which are applied to the switching device 48 at time t7 effectively nullify each other in a manner which will be presently described so that no output signal is applied by unit 4S to ampliiier 92 for translation to the output terminals 42, 42 of the decoder 40.

The negative-polarity pulse applied at time t7 to the control electrode of the normally conductive tube 98 momentarily renders that tube nonconductive, thereby developing a positive-pol-arity pulse at its anode for application to the control electrode of the normally nonconductive tube 101. The last-mentioned pulse renders i l15 Y tube 101 conductive sothat it tends'todevelop a negatives polarity pulse at its anode at time nl.. VYSubstantiallyl simultaneously, the negative-polarity pulse applied to the control electrode of tube 163 at time Vtfzltends to develop a positive-polarity pulse at the anode offthat tube. As a nullify the effect of pulse d, which is the incorrect second.

pulse of the second pulse pair c+d, `and also nullify the elect of pulse c, which is the wrong second pulse of the first pulse pair a-l-c, appearing atrpoints 3 and 5 at timer?.

Fig. 4 also illustrates the pulses appearing at point 9a at point 9a consists ofthe pulses then appearing atV points 6a and 7a in combination with Vany pulse'developed at; the anode of tube 63 and translated by the diodeV 89 as a result of positive-polarityY pulses appearing at points 4 yand at times 't4 and t5. The pulses appearing atV points 6a and 7a are identical with those represented in -'Fig.r4 of the drawings as appearing at points 6 and 7 and, therefore, constitute negative-polarity pulses a-i-c and b|d occurring at times t4 and t6, respectively. At ,time t6 the positive-polarityV pulses c and b are applied by points 4 and 5 to the inner and outer control electrodes of theV tube 68 ofv the repeater S7, thereby developing at its Y l5-microsecond spacings 'and constituting the undesiredrstcode lfipand the undesired second code Ill are ineiective todevelop an output signal in the decoder 4Q eventhough the iirst pulses a and b of the twoipairs and also the second pulses c and d of the two pairs have the correct pulse spacing. Similarly, the decoder 4@ is effectiveto; reject other pulse combinations` having different spacingswhich might combine at random to produce undesired paired pulses having the correct -microsecond spacing.

' As with the lo embodiment of the invention, the operation of the Fig. 3a decoder 40 has been explained in connection with the translation of pulses in networks 49 and 80 only in .the forward direction. Pulses translated Y -at times t4 and t5. The signal appearing at these instants Y anode for translation through diode 89 to point 9a a Y negative-polarity pulse identified in the drawings as b-l-c, which pulse coincides with the pulse b-i-d translated from point 7a. These pulses effectively constitute a single pulse which alters the conductivity of tube 98 and develops at its anode a positive pulse which renders tube 101 conductive. The latter develops ya negative-polarity pulse at its anode. However, the diode 1% is poled so that it cannot translate this pulse to unit 92 andthe output terminals 4Z, 42. SinceV at time t6 there is no coincidence of a pulse appearing `at point 3 with the spulserb at point 5, the coincidence repeater 50 does not develop at time t6 an output pulse forrapplication to the switch# ing device 43. Accordingly, no output pulse isdeveloped by the decoder 4@ at time t5. Y s s Y i Referring to the curves illustrating the pulses applied by points 3V and 5 at time t4 to the control electrodesof the tube 66 oi coincidence repeater 50,` it willibe seen that positive-polarity pulses b and a are Veffective to render 'tube 66 conductive thereby developing at 'its anode for translation through diode 91V and the time-delay network 47 a negative-polarity pulse for application at timer.;V to

'in the reverse direction through these networks do not impair the operation ofthedecoder. Other time-delay devices may also be employed Yin place of the various portions of the networks 49 and 80.

While the decoder of the present invention has been ydescribed in detail in an Vinterrogator-responser, it will beA apparentto those skilled in the art that it also has utility as the decoder of a transponder beacon. Y* Y While there have been described what are at present considered to be, the preferred embodiments` of this invention, it will be obvious to, those skilled in the art that various `changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall 'Within the true spirit and scope of the invention.

What is claimed is:

l. A( pulse-translating system comprising: an input circuit for supplying desired pulse groups having a given Y Veifectively4 responsive to pulses of said other pulse groups pointsll and the control electrode of tube yM3 of'the Y switching device 4.8. The negative-polarity' pulse a-[--c applied at time t4 by point 9a to the inner control electrode of the tube 93 renders it nonconductive'and (in the manner previously described Ainfconnection with the negative-polarity pulse developed Vat time t7 and applied yto the outer control electrode of tube 98), so controls the operation of tube lill at time t4 as to cancel at the interconnected anodes of the tubes 101 andlilcany output pulse which might be developed thereat as the re" sult of the application at time t4 of the negative-polarity pulse to the control electrode of tube N3 from the anode circuit of the coincidence repeater 50. Thus, the negativepolarity pulse a-{Lc occurring at points '9a at time t4 nullifies the effect of pulse vb appearing at point 3 at time Y Y ing that the two interleaved pairs of pulses having for deriving and applying to said device a control signal Which'momentarily opens said switching `device and places said network in a nontranslating condition for pulses at said other -spacings, whereby said system has a'rreduced tendency 'to develop said undesired output signal While deriving said desired output signal. Y

Q.. A pulse-translating systemcomprising: an input circuit for supplyingrdesired pulse groups having a given pulse spacing and subject to the translation of a plurality of other pulse groups having other pulse spacings which may combine at random torproduce undesiredv Y pulse groups having said given spacing; a pulse-trans-V lating network coupled to saidrinput circuit and including a normally closed electronic switching device and,a pulseselector circuit responsive. tov said desired pulse groups for deriving therefrom, a desired output signalbut which tends to respond to and develop from said undesired pulse groups anj undesired output signalgcandV means including control apparatus coupled to said network and said device and effectively responsive to pulses of said other pulseV groups 'for deriving and applying to said device a control signal which effectively momentarily opens said switching device and places said network ina n0nY .translating condition for pulses at said` Vother Vspacings whereby said system has4 a reduced tendency to develop said undesired outputsignal'while deriving said desired output signal. c

3. A: pulse-translating system comprising: an' input circuit for supplying desired pulse groups having a` given pulse spacing and subiect to the translation of a plurality Q Other pulse groups havingother pulse spacingswhich nAi 17 may ,"combine at random to producev undesired pulse groups having said given spacing; a pulse-translating network coupled to said input circuit, including a control device and a pulse-selector circuit comprising time-delay means responsive to said desired pulse groups for deliving therefrom a desired output signal but which tends .to respond to and develop from said undesired pulse groups and undesired output signal; and means including fcontrol apparatus coupled to said input circuit, said timedelay means, and said device and eifectively responsive to pulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said device in a nontranslating condition for pulses at said other spacings, whereby said system has a reduced tendency to develop said undesired output signal while deriving said desired output signal.

4. A pulse-translating system comprising: an input circuit for supplying desired pulse groups having a given pulse spacing and subject to the translation of a plurality of other pulse groups having other pulse spacings which may combine at random to produce undesired pulse groups having said given spacing; a pulse-translating network coupled to said input circuit, including a control device, time-delay means, and a coincidence repeater having an output circuit, responsive to said desired pulse groups for deriving therefrom in said output circuit a desired output signal but which tends to respond to and develop in said output circuit from said undesired pulse groups an undesired output signal; and means including control apparatus coupled to said input circuit, said timedelay means, and said device and effectively responsive to pulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said network in a nontranslating condition for pulses at said other spacings, whereby said system has a reduced tendency to develop in said output circuit to and develop in said output circuit from said undesired y circuit a desired output signal but which tends to respond pulse groups an undesired output signal; and control apparatus coupled to said input circuit, said time-delay network, and said device and electively responsive to pulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said pulse-translating network in a nontranslating condition for pulses at said other spacings, whereby said system has a reduced tendency to develop in said output circuit said undesired output signal while deriving said desired output signalf 6. A pulse-translating system comprising: an input circuit for supplying desired pulse groups having a given pulse spacing and subject to the translation of a plurality of other pulse groups which may combine at random to produce undesired pulse groups having said given spacing; a pulse-translating network coupled to said input circuit and including a control device and a pulse-selector circuit responsive to said desired pulse groups for deriving therefrom a desired output signal but which tends to respond to and develop from said undesired pulse groups an undesired output signal; and means including control apparatus including a plurality of coincidence repeaters having individual input circuits coupled to predetermined portions of said network and having individual output circuits coupled to said device and effec- 18 tively responsive to pulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said network in a nontranslating condition, whereby said system has a reduced tendency to develop said undesired output signal while deriving said desired output signal.

7. A pulse-translating system comprising: an input circuit for supplying desired pulse groups having a given pulse spacing and subject to the translation of a plurality of other pulse groups which may combine at random to produce undesired pulse groups having said given spacing; a pulse-translating network coupled to said input circuit and including a control device, a first time-delay network, and a pulse-selector circuit responsive to said desired pulse groups for deriving therefrom a desired output signal but which tends to respond to and develop from said undesired pulse groups an undesired output signal; and control apparatus including a second time-` delay network coupled to said device and having a delay characteristic corresponding to that of said iirst network, and a plurality of coincidence repeaters having individual input circuits coupled to predetermined portions of said rst network and having individual output circuits coupled to said device and said second network and eiiectively responsive to pulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said pulse-translating network in a nontranslating condition, whereby said system has a reduced tendency to develop said undesired output signal while deriving said desired output signal.

8. A pulse-translating system comprising: an input circuit for supplying desired pulse groups having a given pulse spacing and subject to the translation of a plurality of other pulse groups which may combine at random to produce undesired pulse groups having said given spacing; a pulse-translating network coupled to said input circuit and including a control device, a tirst time-delay network, and a pulse-selector circuit coupled to predey and control apparatus including a second time-delay network coupled to said device and having a 4delay characteristic corresponding to that of said irst network, and a plurality of coincidence repeaters having individual input circuits coupled to predetermined portions of said first network and having individual output circuits coupled to saidv device and said second network and eiectively responsive to pulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said pulse-translating network in a nontranslating condition, whereby said system has a reduced tendency to develop said undesired output signal while deriving said desired output signal.

9. A pulse-translating system comprising: an input circuit for supplying desired pulse groups having a given pulse spacing and subject to the translation of a plurality of predetermined other pulse groups which may combine at random to produce undesired pulse groups having said given spacing; a pulse-translating network coupled to said input circuit, including a control device, a nonreflecting time-delay network having a plurality of network sections individually aording a time delay equal to the pulse spacing of individual ones of said other pulse groups, and a coincidence repeater coupled to predetermined ones of said network sections and having an output circuit, responsive to said desired pulse groups for deriving therefrom in said output circuit a desired output signal but which tends to respond to and develop in said output circuit from said undesired pulse groups an undesired output signal; and control apparatus including a plurality-of coincidence detectors individually coupled to predetermined ones of said network sections Y 19 Y A and to said device and effectively responsive to pulses of said other pulse groups-for` deriving and applying to said device a control signal which momentarily places said pulse-translating network in a nontranslating condition, whereby said system has a reduced tendency to develop in said output circuit said undesired voutput signal while deriving said desired output signal. i

10. A pulse-translating system comprising: an input circuit for supplying desired'pulse groups having a given pulse spacing and subject to the translation of a plurality of predetermined other pulse groups which may combine at random to produce undesired pulse groups having said given spacing; a pulse-translating'network coupled to said input circuit, including a control device, a nonreflecting time-delay network'having a rst network section afford ing a time delay equal to said given pulse spacing and having a plurality of network sections individually affording a ltime delay equal tov the pulse spacing of individual ones of said other pulse groups, and a coincidence repeater coupled to said rs't network section and having an output circuit, responsive to said desired, pulse groups for deriving therefrom in said output circuit a Y v 20 dividual ones of said other pulse groups, and a coincidence repeater coupled fto said iirstY network `section andi having an output'circuit, responsive to said desired pulse groups for 'deriving thereromfin said output circuit a desired output: signal 'but which tends -to respond to and develop in lsaid .output circuit from said undesired pulse groups vanl undesired output signal; and control apparatus including a second time-delay network coupled to said device and having fnetwork sections with delay characteristics corresponding to those of saidlirst network, and a plurality Yof Vcoincidence detectors individually coupled to. individual'onesl of said plurality of network sections, said corresponding network sections, and to said device and effectively responsive `to pulses of said otherV pulse groups for deriving andapplying to said device Ya control signal which momentarily places said device in a. nontranslating condition, whereby said system has a reduced tendency to develop inisaid output circuit said undesired output signal/while deriving said desired output signal. Y 'Y v l 13. A pulse-translating system comprising: an input circuit for supplying desired pulsegroups having a given desired output signal but which tends to respond to and develop in said output circuit. from said undesired pulse groups an undesired outputsignal;` and control appara# tus including a pluralityof coincidence detectors individually coupled to individual ones of said plurality of network sections and to said device and eiectively responsivertopulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said pulse-translating network in a nontranslating condition, whereby said system lhas a reduced tendency to develop in said output circuit said unl desired output signal while deriving said desired output signal.

,11. A pulse-translating system'comprisng: an input circuit for supplying desired pulse groups having a given pulse spacing and subject to the translation of three predetermined other pulse groups which may combine at random to produce undesired pulse groups having said given spacing; a pulse-translating network coupled to said input circuit, including a control device, a nonreiiecting time-delay network having a irst network section affording a time delay equal to said given pulse spacing and having three network sections individually affording a time delay equal to the pulse spacing of individual ones of said other pulse groups, and a coincidence repeater coupled to said rst network section and having an output circuit, responsive to said desired pulse groups for deriving therefrom in said output circuit a desired output signal but which tends to respond to and develop in said output circuit from said undesired pulse groups an undesired output signal; and control apparatus including a plurality of coincidence detectors individually coupled to individual ones of saidy three network sections and to said device and effectively responsive to pulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said pulse-translating network in a nontranslating condition, whereby said system has a reduced tendency to develop in said output circuit said undesired output signal while deriving said desired output signal.

12. A pulse-translating system comprising: an input circuit for supplying desired pulse groups having a given pulse spacing and subject to the translation of a plurality of predetermined other pulse groups which may combine at random to produce undesired pulse groups having s'aid given spacing; a pulse-translating network coupled to said input circuit, including a control device, a rst time-delay network having a lirst network section affording a time delay equal torsaid given pulse spacing and having a plurality of network sections individually affording a time delay equal to the pulse spacing of i11- pulse spacing and subject to the translation of a plurality of other pulse groups which may combine at random to produce undesired pulse groups having said given spacing;,a pulse-translating network coupled to said input circuit and including a control device and a pulse-selector circuit responsive to said desired pulse groups for deriving therefrom a desired output signal but which tends to respond to and develop from said undesired pulse groups an undesired output signal; and means including control apparatus having individual input circuits coupled to predetermined portions of said network and having individual output circuits coupled to said device and including time-delay means coupled to said output circuits and said device and eiectively responsive to pulses of said other pulse groups for deriving and applying to said device a control signal which momentarily places said network in a nontranslating condition, whereby said sys tem has a reduced tendency to develop said Vundesired output signal while deriving, said desired output signal.

14. A pulse-translating system comprising: an input circuit for supplying desired pulse groups having a givenV pulse spacing and subject to the translation of a plurality of other pulse groups which may combine at random to produce undesired pulse groups-having said given spacing; a pulse-translating network coupled to said input circuit and including a control device and a pulseselector circuit responsive to said desired pulse groups for deriving therefrom a desired output signal but which tends to respond to and develop from said undesired pulse groups an undesired output signal; and control apparatus, including a plurality of coincidence repeaters having individual input circuits coupled to predetermined portions of said network and having individual output circuits coupled to said device and including time-delay means coupled to said output circuits and said device, effectively responsive to pulses of said other pulse groups for. deriving and applying to said device a control signal which momentarily places said network'in a nontranslating condition, whereby said system has a reduced tendency to develop said undesired output signal while deriving said desired output'signal.

References Cited inthe tile of this patent UNITED STATES PATENTS 1,763,390 Davis June 10, 1930 2,293,869 Vaughan Aug. 25, 1942 2,444,741 Loughlin July 6, 1948 2,577,141 Mauchly et al. Dec. 4, 1951 2,670,463 Raymond et al. Feb. 23, 1954 2,706,810 Jacobsen Apr. 19, 1955 

